A Brief History
Early Food Preservation
900 AD – “Food Poisoning” Recognized
1795-Appert Developed Canning
1854-1864-FOOD MICROBIOLOGY
BECOMES A SCIENCE
Louis Pasteur
Why Study Food Microbiology?
Provide Clean, Safe, Healthful Food to
Consumer
Food Permits Growth
Control of Microbial Growth
Prevent Food Spoilage
Prevent Food-borne Illnesses
Food-Borne Illness
ERS Estimates
$6.9 Billion/Year Cost of FBI
CDC Estimates
76 Million Cases of FBI Annually
325,000 Hospitalizations
What Organism Causes the Most
Cases of Food-Borne Illness
What Organism Causes the Most
Deaths Due to Food-Borne
Review of Microbiology
Mostly Single Celled
Groups
Morphologies
Gram Reactions
Size
Exponential Growth
30 Minute Generation Time
Time 0
1000/g
30 min
2000/g
1 hour
4000/g
……..
Microbial Growth Phases
A B C D A=Lag Phase B=Log/Exponential Phase C= Stationary Phae D= Death Phase TimeIntrinsic and Extrinsic Factors
Intrinsic
pH
Moisture Content
Oxidation-reduction Potential
Nutrient Content
Antimicrobial Constituents
Biological Structures
pH
Effects of pH
Enzymes
Nutrients
Other Environmental Factors
Temperature
Salt
Age
No known pathogen grows below pH of 4.6
Moisture
Remove and/or Bind Moisture
Humectants
Dehydration
Water Activity – Aw
Most Fresh Foods - Aw > 0.99
0
1
Pure water
No water
Microbial Growth and Aw
Halophilic
0.75
Xerophilic molds
0.61
Osmophilic yeasts 0.61
Lowest Aw for Pathogen Growth
0.86
Oxidation- Reduction Potential
O/R Potential - Eh
“…ease with which the substrate loses or gains
electrons.”
Loss of electrons – oxidized
Gain of electrons – reduced
Aerobic
Anaerobic
Microaerobic
Others
Nutrients
Fastidius vs non-fastidious
Biological Structure
Antimicrobial Factors
Extrinsic Factors
Temperature
Relative Humidity
Gases in the Environment
Temperature
Microorganisms grow over a wide range of
Temperatures
Psychrotrophs
Mesophiles
Thermophiles
Psychroduric
Thermoduric
Other Factors
Relative Humidity of Environment
Can change the Aw
Environmental Gasses
Presence of Other Microorganisms
Competitive Exclusion
General microbial antagonism
Lactic Antagonism
Hurdle Concept
Combine Intrinsic and Extrinsic Factors to
Control Microbial Growth
Combination requires less severe treatments
Food Microbiology
Microorganisms as causative agents
of disease in Humans--Foodbourne
pathogens
Microorganisms and Food spoilage
Microorganisms as Food sources
Microorganisms exploited for the
production of food
What is microbiology
Study of Micro-organisms: Organisms that EXIST as Single Cells or cell clusters and must be viewed individually with the aid of a Microscope
1. EXIST (Webster definition)To continue to be, have life; live
HALLMARKS OF LIFE 1. METABOLISM 2. DIFFERENTIATION 3. REPRODUCTION 4. COMMUNICATION 5. EVOLUTION
2
.
KEYWORD
single
CELLS
(OR cell clusters)
CHARACTERISTICS THAT MICROORGANISMS HAVE THAT MAKE THEM TRUE CELLS
1. CELL MEMBRANE –barrier that separates the inside of the cell from the outside
2. NUCLEUS OR NUCLEIOD – location of genetic information (DNA)
3. CYTOPLASM –location of the machinery for cell growth and function
4. MACROMOLECULES – proteins, nucleic acids, lipids, polysaccharides
3
.
KEYWORD
exist as
SINGLE
cells
(OR cell clusters)
We are multicellular creatures—made up of many cells
What makes one of our cells different from a TRUE microbial cell??
A single microbial cell can have an independent existence—our cells need to other cells in order to carry out their cellular
What organisms are studied in food
microbiology
1. BACTERIA—*
2. FUNGI—molds and yeasts *
3. ALGAE—dinoflagellates/shellfish *
4. PROTOZOA—amoeba, Giardia *
5. Viruses—Hepatitis/shellfish 6. Prions
7. Helminths—worms
Taxonomy
The study of phylogenetic relationships between organisms
(The sorting of all living things based on their related or differentiating features)
KINDOM the highest level in classification PHYLUM related classes
CLASS related orders ORDER related families FAMILY related genera
GENUS closely related species
SPECIES organisms sharing a set of biological traits and reproducing only with their exact kind
Further classifications especially with bacteria and yeasts
Strain—organisms within a species varying in a given quality
Genus, Species, Strain and Type
All living organisms have a first name and a second name: The first name is always capitalized (Genus)
The second name is always denoted in lower case letters (species)
Both names are always italicized or underlined
Example
Lauren brandon or Lauren brandon
Strain refers to a genetic change made in an organism that makes it different from the predominant species organism
Type refers to surface changes that make the organisms distinguish able from others of its species
Scope of study in Food Microbiology
1. BACTERIA--bacteriology 2. FUNGI--mycology
3. PROTOZOA—parasitology 4. ALGAE
5. VIRUSES--virology (although not a cellular entity but an intracellular parasite)
6. WORMS—parasitology (helminthology) --not true micro-organisms—but included in food/medical microbiology
7. PRIONS—pathogenic neural derived proteins
8. EPIDEMIOLOGY—study of the source and prevalence of disease
Why study Food Microbiology??
Microorganisms as causative agents of
disease in humans--foodbourne pathogens
Microorganisms and food spoilage
Microorganisms as food sources
Microorganisms exploited for the production
of food
Agents of Disease (Foodbourne Pathogens)
BACTERIA E coli O157:H7, Salmonella spp., Vibrio cholera,
Bacillus cereus, Clostridium botulinum, Listeria monocytogenes, Staphylococcus aureus
VIRUSES Enteroviruses, Norwalk virus, Hepatitis virus
PRIONS Mad Cow Disease (BSE) and Creutzfeldt-Jakob Disease PROTOZOA Giardia lamblia, Cryptosporidium parvum, Entamoeba
histolyticum, Cyclospora cayetanesis
HELMINTHS Tapeworms (Beef, Fish and Pork), Flukes (Fish and Shellfish), Roundworms and Hookworms
Food Spoilage
Fungi— Bread and Cheese Mold
Bacteria— Erwinia caratova soft
rot in carrots and cucumbers
Microbes we can eat
Fungi: Mushrooms are actually a microorganism— although the fruiting body is macroscopic!!!
Yeasts: Vegemite (Yeast Paste)
Bacteria: Spirulina platensis (a cyanobacterium)
Microbes that we can exploit
Bacteria—cheese, yogurt, vinegar, bread and sauerkraut production
Yeasts—bread, beer, liqueurs, wine
Bacteria in agriculture
Rhizobium spp: Nitrogen fixation in root nodules of legumes
alfalfa etc.
Bacteria used in engineering produce that is resistant to
